Vertical blanking circuit for television transmitter systems



May 31, 1949- 0. H. SCHADE 2,471,903

VERTICAL BLANKING CIRCUIT FOR TELEVISION TRANSMITTER SYSTEMS OriginalFiled Deo. 3l, 1941 ma. 75o Il m 2 wil/[1:7443

BY 'N75 TSM/vw.

ATTORN EY Patented May 31,1949

VERTICAL BLANKING CIRCUIT FOR TELE- VISION TRANSMITTER/SYSTEMS Otto`lll. Schade, West CaldwelhN. J., assignor` to` Radio Corporation ofAmerica, a corporation of Delaware Original application-December 31,1941, Serial No.

425,088. Divided and this application December 29, 1944, Serial No.570,369

3 Claims.

1, This invention is a division of U. S. Patent toi Otto H. Schade, No.2,402,091, filed December 3l,` 1941, issued June 11, 1946,` and relatestoan.y

improvement in-` television.` systems; More particularly, the presentinvention relates to an.I improvement in systems for generatingsynchronizing signals, blanking` impulses, andthe necessary deflectionvoltage variations for use in a television transmitting, apparatus.

ln` present-day television systems the receiving apparatus aremaintained in, synchronous.l

operation with the transmitting apparatus by; means of: transmittedhorizontal and vertical'` synchronizing signals. These signals arenormally` transmitted `along with the picture signals, the picturesignals and the synchronizing signals being used to modulate a singleradio frequency carrier wave. In order that the synchronizing sign-alsmay be interspersed with` the picture signals, the picture signals vareentirely eliminated during periods of synchronization and in lieu of.theeliminated picture signalsthe desired vertical or. horizontalAsynchronizing signals are transmitted. It is also conventional practiceto. transmit the synchronizing signals in such a direction that they arein the direction of black` in' the picture and extend further in that`direction than `the blackest black (i. e., they are blackerthan-black)so that when the composite series istapplied to a television receivingtube the synchronizing signals will inherently cause blanking ofthecathode ray beam in the receiving tube during return deflectionintervals.

Various systems' have been used for producing the desired blanking,synchronizing and deflection voltage variations that are necessary atthe transmitter but in most instances such systems are rathercomplicated and involve :a considerable number of tubes and .circuitcomponents. `Furthermore, in some systems,` considerable additionalcircuit arrangements have been included in order to` transmit impulsesof double horizontal deilection `frequency immediately preceding,during, and immediately following the transmis--y sion of the verticalsynchronizing impulse. Such transmission is generally known as slottedvertical synchronizing and .although the use of such a synchronizingmethod has certain advantages it` has been found that by using thecircuits of thev present invention, as herein described for instance, itis not necessary to include the socalled double line frequencypreparatory impulses nor is it necessary to slot the verticalsynchronizing impulse at double line frequency. In the absence of suchslotting and `in the absence of the double line preparatory impulses thehorizontal deection` generator may momentarily lose synchronism;however, synchronous operation of the horizontal oscillator will beresumed almost immediately following the verticalusynchronizing impulseperiod. Furthermore, it has been found, that adequate interlacedscanning at both the` transmitter and the receiver maybe accomplished,

even in the absence` of the use of the double` line frequency impulses.

It is thereforeone purpose of the present invention to provide a new,improved and simplified; synchronizing signal and wave form generatingysystem which includes a relatively small` number` of tubes and circuitvelements and which` will produce a picture ,and synchronizingsignalseries which is entirely effective to maintain synchronous operation ofall-receivers tunedto the trans.-y mitting station.

Another purpose of the present invention resides inthe provision of `asimplified systemy for producing the necessary picture signal seriesblanking impulses and the necessary horizontaland vertical synchronizingimpulses that are transmitted during the blanking period.

Still another purpose` of the present invention resides inthe provisionof means for simultaneously generatingdefiection voltage Variationswhich may be used to directly cause deflectionv of the scanning cathoderay beam in the television transmitting tube or which may be used,v todrive a power tube for deflecting the scanning cathode ray beam.

Still a` further purpose ofI the present inven-` tion resides in theprovision, of Ia circuit for generating voltage variations which may beused to deflect a cathode ray beam in a monitoring oscilloscope.

Another purpose of the present invention resides in the provision of acircuit for generating voltage variations of saw-tooth wave form thatmay be, used to `control devices for producing shading control signals.

A still further purpose of the present invention resides in theprovision of a circuit arrangementJ which will produce the above`referred to voltage variations in response to` the application` ofproperly timed horizontal and Vertical synchronizing impulses.

Alstill further purpose of the present invention resides intheprovisionl of a circuit arrangement for producing a desired compositepicture and synchronizing signal series which may be used` directly` tomodulate a radio frequency oscillator in order that the composite signalmay be transmitted to` a remote receiving station.

Still other purposes and advantages of the present invention will becomemore lapparent to thoseskilled in the art from the followingspeciiication and drawings wherein the single figure represents apreferred form of the present invention. Furthermore, the ligure alsoshows various curves of` voltage variations appearing at various partsof the circuit.`

For controlling the apparatus and circuit arrangement shown in thesingle figure and` described in the following specification, a source ofhorizontal and vertical synchronizing impulses must be provided. Such asource is not shown in the drawing and it is to be understood that thehorizontal and vertical synchronizing impulses may be derived from anyappropriate generator. It is only necessary that the horizontal andvertical synchronizing impulses be of the desired frequency and bespaced with respect to each other by the desired amount. By way ofexample, a generator for supplying such impulses is shown and describedin Schade Patent No. 2,254,626, issued on September 2, 1941.

Referring now to the drawing, the picture signals which are derived froma television transmitting tube are applied to terminals I6 and II, thelatter of which is connected to ground. These signals may be derivedfrom any desired television transmitting tube. The horizontalsynchronizing impulses from any appropriate source may be applied to theterminal I2 while the vertical synchronizing impulses are applied to theterminal I4.

The system includes discharge tube I6, which in turn includes cathodesI8, two control electrodes 20 and 22, and two anodes 24 and 26.

These elements may be enclosed in a single tube envelope (as shown) orthey may constitute the elements yof two separate triode ormulti-electrode tubes. The elements are connected as a multi-vibratorand the operation of the multivibrator is synchronized by means ofhorizontal impulses which are applied to the terminal I2 from anydesired appropriate source. The impulses which are impressed upon theinput terminal I2 are applied to the control electrode 26 throughcoupling condenser 28.. The control electrode 2|) is connected to groundby way of the usual grid resistor 30 and in order that the controlelectrode may be operated at a proper potential with respect to cathodeI8 a resistance 32 is also included between the control electrode andterminal 34 to which a positive potential is applied. The positivesupply potential that is applied to terminal 34 is de-coupled from theelements of tube I6 by de-coupling resistance 36 and condenser 38. Theanodes 24 and 26 are also connected to the positive terminal 34 by wayof anode load resistance 40 and 42, respectively. The anode 24 iscoupled to the control electrode 22 by means of coupling condenser 44while the control electrode 22 is connected to the cathodes I8 by meansof resistance 46 and potentiometer 48. One end of the resistance elementof the potentiometer 48 is connected to the resistance 46 whereas theother end of the resistance element of the potentiometer, as well as themovable contact thereof, are connected to the cathodes I8. The anode 26is connected to output terminal 50 and to ground through condenser 52while the control electrode 22 is connected to output terminal 54 by wayof resistance 56. The resistance 56 has connected in parallel therewitha condenser 58. The cathodes I8 are connected to ground by way ofvariable resistance 6I and inductance 62 while the inductance 62 hasconnected in parallel therewith a resistance 63. The purpose ofproviding the inductance in the cathode circuit of tube I6 is to providean inductive feedback impedance in order that short impulses of highamplitude may be produced. The widths of the produced imipulses may bereadily controlled by varying the amount of the resistance 6I whichvcontrols. the cathode impedance. The speed of 4 operation of themulti-vibrator which includes the elements of tube I6 may be controlledby adjusting the potentiometer 48.

When horizontal synchronizing impulses are applied to the'terminal I2with the impulses extending in a negative direction, electronic currentfrom cathode I8 to anode 24 is reduced during application of theindividual impulses. This reduction in anodic current causes positiveimpulses to appear at the anode of tube 24 and these impulses areapplied to the control electrode 22 of tube I6 through condenser 44. Theheavy cathode current that is caused to flow drives the cathodes in apositive direction causing the current to anode 24 to be completelycutoif and since the anode 24 is connected to terminal 60, the strongimpulses produced at anode 24 are then available at terminal 6I) and mayhave a wave form such as that represented by the curve 65. Naturally theimpulses extend in a positive direction and occur at a frequencycorresponding to the synchronizing impulses applied to the controlelectrode 20 but of a time duration (or width) determined by theresistance 6I.

The circuit also provides a source of deflection voltage variationswhich may be derived from terminal 54 and which may have a wave formsimilar to that shown by curve 64. These impulses are derived from thecontrol grid 22 and the parallel resistance and condenser combinationy56-58 are included between the control electrode 22 and the terminal 54in order to produce wave shaping (and biasing of the following tube) toprovide the desired voltage variation or wave form. It will be noticedthat this wave form is substantially that necessary for driving a powertube for supplying horizontal deflection voltages for deflecting thescanning cathode ray beam in an Iconoscope or similar televisiontransmitting tube where electromagnetic deflection is used.

When condenser 52 is connected between the anode 26 and ground, thetriode section including anode 26 of tube I6 operates as a dischargetube as well as a part of the multi-vibrator with the result thatvoltage Variations of substantially sawtooth wave form may be obtainedfrom the anode 26. As stated above, these voltage variations areavailable at terminal 50 and may have a wave form corresponding to thecurve shown at 66. In so far as this part of the operation is concerned,the condenser 52 charges through load resistance 42 and de-couplingresistance 36 and is discharged by current ilow between cathode I andanode 26.

From the above it may be seen, therefore, that` the single tube I6,together with its associated circuit elements, operates both as amulti-vibrator and as a discharge tube for producing several sources ofvoltage Variation. From the terminal 6I] may be derived horizontalblanking impulses of a width determined by the resistance 6I while fromthe terminal 54 may be derived voltage variations of a wave form such asare suitable for driving a horizontal deflection power tube.Furthermore, the saw-tooth wave form Voltage variations which arederived from terminal 50 may be conveniently used for horizontallydeilecting the cathode ray beam in an oscilloscope tube, particularlywhere the cathode ray beam of the oscilloscope is electrostaticallydeflected. This voltage, as stated above, may also be used to control ashading signal generating device.

A somewhat similar circuit arrangement .is alsoprovided for producingsimilar voltage variaatentos 'tions at vertical deiiection frequency.This cirfcitarrangement includes tube 68 which inturn indludes cathodescontrol electrodes `'|2 and "Tllaswell 'asanodes 'T6 andf'l. Theelements "fofftlie tube68are connected asa multi-vibrator ""the"operationof the multi-vibrator is synhronized by vertical synchronizingsignals ap- Yplied to the 'terminal M. Resistances 30, 82 andf`i6`4"`ar`e connected inseries and the series arrangeent "is connectedfrom input terminal |4 to round. The control electrode '|2 is connectedto 1the "junction fof 'resistance 82 Aand 34 by `means of seriesconnectedresistance 86 and condenser v"88; Furthermoraa condenser 96 isconnected betWeen the control relectrode 'l2 and ground. -"Ihe inclusionof the resistance 86 and the condenser 9[|"provides a time delay circuitin order that the vertical synchronizing impulses which "are applied tothe terminal I4 will be delayed by fa predetermined amount before beingapplied to 'the control electrode "|2. The anode 16 is "connectedtoiterminal 35, to Which is applied a "positivepotential, by means ofload resistance 92, potentiometer 94 and de-coupling resistance 96.,infile-coupling condenserQB is connected betweenthejunctionofpotentiometer 94 and de-coupling resistance-S6 while the`movable contact of the fpotentiometer'Bfl is also connected to thejunc- "tionofthe potentiometer and the de-coupling resistance"`96`.Theanode 18 is also connected to @the de-coupling resistance by means ofpo- `ftentio-Jn'ieter-Iiltl The cathodes 'lll are connected to'groun'dby way of cathode resistance |02, the resistance being bypassedby condenser |04 in 1order to round off the front edge of thefeediback'impulse. This action, in so far as the feedback is concerned,is effective to prevent unstable triggering of the circuit and greatlyinfcreases the stability of interlace. Voltage varia- Ltions which arepresent at the anode '|6 are "ap'pliedtothe control electrode 'M by wayof coulpiling condenser |64 while the control electrode |"4"'isconnecteditoground by Way of resistance l`|`|f|ia`nd potentiometer |08.The potentiometer ""IUS `is connected as a variable resistance and iseffective to control the free operating speed of the multi-vibrator.

Theivertical synchronizing impulses which are "applied to terminal i4are also applied to the control electrode of tube I0. riorthis tube isconnected tothe junction of re- "isistance 80 andfl by means of seriesconnected "resistance vl |2 and condenser H4. The voltage VariationsWhich are applied to the control electrode of tube l) are therefore notdelayed and "precede the'voltage variations which are applied "tothecontrol electrode l2 by` a predetermined ""amount. The controlelectrodeof tube H0 is also connected to groundby a usual grid resist- "ance H6.The cathode of tube ||6 is connected "jto ground by cathode resistanceH8 While the "fanode of the tube is connected to the positiveftiezrminal 34 by means of anode load resistance 0.

`When vertical synchronizing impulse signals fareapplied to the controlelectrode l2 of the multi-vibrator tube 68 after a predetermined timedelay, the operation of the multi-vibrator is controlled andsynchronized with the vertical "synchronizing impulsesand the circuitoperates Atoproduce at the anode '|6 delayed voltage variahltionsWhichextend in a positive direction. These voltage variations arepresenten conductor |22 fand-are appliedto a further delay circuitincluding resistances |24 and |26 as Well as condensers The control`electrode 6 :|28 and L| 30. Thecombination of resistance |254 and`condenser^|28 as well as'the combination of resistance |26 and`condenser |30 lprovide a further 'time delay lfor the voltagevariations present at anode T6 and these delayed voltage variations arethen available at conductor |32. The wave form ofthedelayedvoltagevariations may have a Wave formsimilar to that shown at curve |34.Theianode of tube |||l is connected to conductor |32 b y `means ofresistance and since the voltage variations appearing at the anode oftube `||`l) are not delayed, these voltage variations when combined withthe delayed voltage `variations from the anode of tube i6 produce avertical blanking impulse such as shown at curve |38 the duration ofwhich is sulicient toprovide `the necessary vertical blanking.

Furthermore, the multi-vibrator including tube 68 and its associatedcircuit elements also produces voltage Variations which are available atthe control electrode 'I4 and which are applied to terminal |40, thesevoltage variations being similar to those shown by curve |42 andsuitable for energizing a vertical deflection power tube. These voltagevariations are therefore similar^ to'the voltage variations whichareavailable at terminal 54`and may-be ultimately used in deflectingthecathode ray beam in the television'transmitting tube, particularly wherethefbeam isdeected'by electromagnetic means as is vanode L78.Actually,"these voltage variations are available from the movablecontact'of potentiometer |66 and are applied to terminal lM6.

They may have a Wave form such as that shown lby curve |48.Asexplainedabove, these voltage 45.v

variations of sawtooth Wave form may be conveniently 'used for 'deectingthe cathode ray beam in an oscilloscope particularly Where electrostatic'deflectionis used.` The voltage variations rnay be useddirectly orafter appropriate amplification. Theymay also be used to controlvertical shading tubes.

From the circuitas so far described, it may be seen that very simple andconvenient circuit arrangementhas been provided for generating`horizontal and vertical blanking impulses and for simultaneouslygenerating horizontal and vertical deflection driving voltagevariations. These deflection driving voltagevariations, afterappropriate amplification, may be used to deneet the cathode rayv beamin the television transymitting tube.

=mustibe suppressed at'various regularly spaced intervals in order thatthe suppressed picture signalsfmaybe replaced by the desired horizontalAand vertical synchronizing signals. The circuit (arrangement forproducing the desired blanking and for interposing the desiredsynchronizing signals includes tubes |50, |52 and |54. Of these sertiontube.

. with condenser |02.

. trol impulses.

vat'arrpos rtubestube |50 is the picturesignal blanking tube whereastube |52 is the synchronizing signal in- Both tubes when supplied withproper voltage variations operate to produce the final composite pictureand synchronizing signal series.

Tube |54 includes cathodes |56, control electrodes |58 and |60 as wellas anodes |62 and |64. The cathodes |56 are connected to ground whilethe control electrodes |58 and |60 are connected to ground by Way ofgrid resistors |66 and |68, respectively. The anodes |62 and |64 areconnected to the positive terminal 34 by load resistances |l and |72,respectively.

The horizontal blanking impulses which are available at terminal 60 andwhich are derived from the anode 24 :of tube I6 are applied to thecontrol electrode |50 by way of coupling condenser iit. Likewise,thevertical blanking impulses Which are available on conductor |312 areapplied to the control electrode |60 by coupling condenser H6. Both thehorizontal and the vertical blanking impulses have their voltagevariations extending in a positive direction to cause modulation ofanodic current in tube |54. Since .the blanking impulses extend in apositive direction, the voltage variations at the anodes |62 and |64will extend in a negative direction upon ,the application of theblanking impulses to the control electrodes |58 and |60. The anode |62is connected to the anode |64 by means of a tune circuit includinginductance |18 and capacitance |86, this combination being connected inseries The purpose of the inductance |70 and the condenser |80 is toimprove the wave form of the horizontal blanking con- If desired, theseelements may actually be omitted, in which case the anodes |62 and |64are directly -connected together and a single common load resistance |12is used. The voltage variations from the anodes |62 and |64 are combinedand are applied to the suppressor grid or electrode of tube |50 by wayof coupling condenser |05. The wave form of the combined blankingcontrol impulses may be similar to that shown at |86. The screen grid oftube |150 is connected to positive terminal 34 by way of resistance |80and potentiometer |90. The resistance element of the potentiometer |90is connected between positive terminal and ground whereas the movablecontact of the potentiometer is connected to the screen grid resistor|88. The screen grid is de-coupled for relatively rapid vvoltagevariations by means of condenser |92.

The cathode -of tube |50 is connected to ground by an unbypassed cathoderesistance |94, particularly if good white signals are available and .ifthe television transmitting (camera) tube is operated at normal gamma.conditions, and where a transmitting tube similar Under low light to anIconoscope is used, a bypass condenser may be used to preventdegeneration and to increase the intensity of picture signalsrepresentative of white. The control electrode is also connected toground by an appropriate grid resistance |96. The anode of tube |50 isconnected to positive terminal 3ft by means of an appropriate load cirlresistance |08 and 200 is connected to the sup- Issor electrode by meansof a further resistance Whenpicture signals are applied to the controlelectrode of tube |56 by Way of condenser 204 they operate to modulatethe electron stream in that tube. The picture signals as appliedtoterminal i0 are polarized such that black in the picture isrepresented by a change in the negative direction whereas white in thepicture is represented by a voltage change in the positive direction.Accordingly, when signals representing black are applied to the controlelectrode of tube |50, the voltage variations at the anode of that tubewill extend in a positive direction. In order to afford the desiredblanliing at horizontal and vertical deflection frequency, the voltagevariations which are applied to the suppressor electrode by way ofcondenser |84 from anodes |62 and |54 of tube G54 are effective tocut-off the current flow through tube E50. As stated before, the voltagevariations from the anodes |62 and |64 extend in a negative directionand are sufficiently intense to reduce the anode current in tube |50 tozero. Accordingly, during such blanking intervals, applied picturesignals are ineifective to produce any potential change at the anode oftube i556 which is driven to its most positive potential. The height ofthe blanking pedestal or, in other words, the potential change of theanode of tube i5@ during blanking intervals may vbe controlled anddetermined by the position of the movable contacts on potentiometerWhich .controls the energizing potential in the screen grid electrode oftube F50. The signal at the output of tube |50 therefore represents thepicture signals applied to terminal I0 with certain intermittentportions of the picture signals being .suppressed or driven to a valuerepresentative of black in the picture.

t is the function of the synchronizing signal vinsertion tube i52 tosuperimpose upon the blanking signal the actual synchronizing signalswhich extend in the direction of black and which correspond to blackerthan black in so far as their intensity is concerned. The synchronizingsignals are not delayed with respect to the front edge of the blankingimpulse as is the practice in some synchronizing systems since it hasbeen found that the front edge of the synchronizing impulse and thefront edge of the blanking impulse may coincide without producing anyundesired results.

Tube |52 includes a cathode, a control electrode,

a screen grid electrode, a suppressor electrode and an anode. Thecathode oi the tube is connected directly to ground whereas the controlelectrode is connected to ground by resistance 206 in parallel withwhich is connected a condenser 208.

The suppressor electrode is also connected to ground by resistance 2idand is coupled to a suppressor electrode of tube |50 by way of couplingcondenser M2. The horizontal synchronizing signals are then applied tothe suppressor electrode of tube |52 from the blanking tube |54 but inthis connection is included condenser 2|2 and resistance 2&0. Theseelements perform a differentiating action to diierentiate the horizontalblanliing impulse to thereby produce a shorter horizontal synchronizingimpulse. There therefore appears on the suppressor electrode of tube |52the horizontal synchronizing impulse which is in fact the differentiatedhorizontal blanking impulse. The vertical synchronizing impulse isapplied to the rst control electrode or control grid of tube |52 bymeans of resistor 2|4 and condenser 2|6 which are connected between thecontrol electrode of tube |52 and terminal |4 einem,

to which. is applied the controlling vertical svnchronizing impulse.vlIwhle same signals that are used to control theVf-ltical multivibratortube 611 are, therefore 'usedto supply vertical. synchronizing impulsestothe control electrode of tube |52.

Since the horizontal synchronizing impulses that are appliedA to thescreen grid electrode |52 and the vertical synchronizing impulses thatare applied to the control electrode of tube |52 extend in a negativedirection, these impulses operate to reduce the current ovv through`tube |52 with the result that the anode is driven in a positivedirection during suchintervals.

The` screen gridv of tube |52 is connected to the movable contact of apotentiometer 2 i8. One end of the resistance element of thepotentiometer ZIB is connected to ground whereas the other end of theresistance element isconnected to the, positive terminal 34y by Way of.resistance 22B. This permits the application `of a predeterminedrelatively small positive potential to the screen grid electrode, thevelectrode being by-passedl to ground in so far as `alternating currentpotentials are concerned by condenser 222. An adjustment of the value ofthe potential applied tol the screen grid electrode which is madepossible by an adjustment of potentiometer 2 3 determines the height orintensity of the synchronizing signal impulses appearing at the anode oftube 52.

The anodes of the blanking tube i553 and the synchronizing signalinsertion tube |52 yare connected together and are in turn rconnected topositive terminal 34dl through series connected inductance 224, afurther inductance `226, a resistance 228 and 23!4 in order to stabilizethe voltage applied to the anode vload circuit oitubes L50 and |52.. An`output circuit is provided between ground and the junction ofinductances 224 and 226 through condenser 234 so that the output energyis available from terminals 236i The inductance 224 is paralleled by aresistance 23B in order to slightly modify the Wave form at the outputterminals.

It may be seen therefore that picture signals when applied to thecontrol electrode of tube |50 cause a corresponding voltage drop loadresistance 22.8 to produce amplified voltage variations at the outputterminal 23S. The horizontal and vertical` blanking impulses which areapplied to the screen grid electrode of tube |53 reduce the current flowthrough. that tube to zero, withy the result that the potential at theoutput terminal 236 is altered in a positive direction. The platecurrent of the parallel synchronizing insertion tube |52 also causes avoltage drop in the common load circuit resistanceo228. The platecurrent ratio of `tube |52 to-tube 151| determines the ratio of thesynchronizing signals (supersync) to blanking. rIlhis ratio can becontrolled, as stated above,` by varying the screen potential applied.to tube |52 by means of potentiometer 2ML The vertical. synchronizingimpulses, as stated above, are applied directly to the control electrodeof tube L52 accordingly. cause tube |52 to be driven to cut-ofi duringvertical synchronizing intervals. During this time no horizontalsynchronizing impulses are present and accordingly no horizontalsynchronizing signals are transmitted during the transmission of theuertical synchronizing signals. The inclusion of the inductances 224 and22B prevents a loss of the high frequency components of the signalseries.

Preferably tubes |50 and |52 should be of the high gain type such as,for example, tubes 6AC'7 mitted.

The circuit shown in the drawing and described above is particularlyadapted for portable television equipment and provides the necessaryvoltage Variations for operating such equipment. The principal elementsnecessary in addition to the circuit described are naturally a source ofpicture signal, a source of horizontal and vertical synchronizingimpulses and a source of radio frequency energy particularly Where radiotransmission is desired. `With these additional elements it is possibleton transmit television images andto, in addition, monitorsuch`transmission by means of the usual, cathode ray oscilloscope.

The horizontal and vertical synchronizing mpulses which are applied toterminals |'2 and` i4; may be derived from` any desired source or, in

fact, these signals may be supplied from the main television transmitterso that they are properly related to the 60 cycle power supply line. Thehorizontal and vertical synchronizing impulses may be transmitted to theportable equipment from the main transmitter by theuse of a separatecarrier for thatpurpose or such signalsmay be separated from thetelevision signal transmitted from the principal transmitting station.The picture .signals may be derived from any television transmittingtube such as, for example,` an Iconoscopej an Orthicon or a Monoscope. i

Since the monitoring oscilloscope is generally. relatively small and it`has a screen of about 3` inches in diameter, the electron beamy in sucha tube is normally electrostatically deflected and,V accordingly, thevoltage Variations of saWtooth Wave form which are `available atterminals 5U. and |46' may -be conveniently used for horizon` tally andvertically deflecting the cathode ray beam in the monitortube, If it isdesired to observe only the signal trace in the monitor tube then thehorizontal deflection of a cathode ray beam therein may be produced byeitherthehorizontal or vertical deflection voltage while the verticaldeflection of the `cathode ray beam may be produced as a function` of4energy derived from the output terminals v236.

From the above it may be seen that a relatively compact andsimplii'ledrsynchronizing signal generator has been provided which operates toproduce not only the desired blanking and synchronizing impulses butalso produces voltage variations which maybe used to deflect the cathoderay beam in the `television transmitting tube. Furthermore, the samesystem provides means for generating voltage Variations of sawtooth Wave.form in order that a monitoring cathode ray tube maybe used at 4theportable transmitter-` The system described also `operates to blank thepicture signal series `at predetermined intervals and to supelmpose uponthe blanking signals the desired synchronizing signals in order that acomplete composite series of picture and syncbronizinc.r signals may beproduced.

The vertical synchronizing impulses may be of any desired length but itis preferable if their length is chosen to equal approximately one linedeflection duration as shown by the curve applied to the outputterminals 236 in order to reduce the possibility of the horizontaldeflection generator in the receiver from momentarily dropping out ofsynchronism. Vertical synchronizing signals persisting for only one-halta line may even be used Without resulting in any difficulty insegregating the horizontal and vertical synchronizing signals.

Although the system is described in more or less detailed form it is tobe understood that various alterations and modications may 'be madetherein and any and all such modifications are to be considered Withinthe purview of the present invention except as limited by thehereinafter appended claims.

I claim:

1. A television transmitting system including a source of verticalsynchronizing impulses, a multi-vibrator including means for generatinga first electron discharge stream, means for generating a secondelectron discharge stream, each means including a cathode, a controlelectrode and an anode, means including separate load impedances formaintaining said anodes positive with respect to their associatedcathodes, a condenser for coupling the anode of the rst electrondischarge stream to the control electrode of the second electrondischarge stream, means including a time delaycircuit for applying thevertical synchronizing impulses to the control electrode of the rstelectron discharge stream to produce delayed voltage variations of apredetermined adjustable amplitude and duration at the associated anode,an electron discharge tube including a cathode, a control electrode andan anode, a load impedance for maintaining the anode of said electrondischarge tube positive with respect to its cathode, means for applyingthe undelayed vertical synchronizing impulses to the control electrodeof said electron discharge tube to produce voltage variations of apredetermined adjustable amplitude and duration, means to further delaythe produced delayed voltage variations, means for combining the furtherdelayed voltage variations produced at the ano-de of the iirstelectrondischarge stream with the voltage variations produced at the anode ofsaid electron discharge tube to produce vertical hlanking impulseshaving a predetermined amplitude and time duration, and a condenserconnected between the anode of said second electron discharge tube and apoint of fixed potential whereby voltage variations of substantiallysawtooth Wave form may be derived from the anode of said second electrondischarge tube.

2. A television transmitting system including a source of verticalsynchronizing impulses, a multi-vibrator including means for generatinga rst electron discharge stream, means for generating a second electrondischarge stream, each 'means including a cathode, a control electrodeand an anode, means including separate load impedances for maintainingsaid anodes positive with respect to their associated cathodes, acondenser for coupling the anode of the rst electron discharge stream tothe control electrode in the second electron discharge stream, meansincluding a time delay circuit for applying the vertical synchronizingimpulses to the control c 12 electrode in the first electron dischargestream to produce delayed voltage variations of a predeterminedamplitude and duration at the anode of said electron stream, circuitmeans to further delay the produced delayed voltage variations, anelectron discharge tube including a cathode, a control electrode and ananode, a load impedance for maintaining the anode of said third electrondischarge tube positive with respect to its cathode, means for applyingthe undelayed vertical synchronizing impulses to the control electrodeof said electron discharge tube to produce voltage variations of apredetermined amplitude and duration, and means for combining thefurther delayed voltage variations produced at the anode of the firstelectron discharge stream with the voltage variations produced at theanode of said electron discharge tube to produce vertical blankingimpulses having a predetermined amplitude and time duration.

3. A television transmitting system including a source of verticalsynchronizing impulses, a multi-vibrator including a first and a secondelectron discharge tube, each including a cathode, a control electrodeand an anode, means includlng separate load impedances for maintainingthe anodes of the electron discharge tubes positive with respect totheir associated cathodes, a condenser coupling the anode of the firstelectron discharge tube to the control electrode of the second electrondischarge tube, means including a time delay Vcircuit forapplying thevertical synchronizing impulses to the control electrode of the firstelectron discharge tube to generate delayed voltage variations of apredetermined amplitude and duration at the anode of said tube, circuitmeans to further delay the produced delayed voltage variations, a thirdelectron discharge tube including a cathode, a control electrode and ananode, a load impedance for maintaining the anode of said third electrondischarge tube positive with respect to its cathode,`

means for applying the undelayed vertical synchronizing impulses to thecontrol electrode oi the third electron discharge tube to generatevoltage variations of a predetermined amplitude and duration at theanode of said tube, means for combining the further delayed voltagevariations generated at the anodes of the lirst and the third electrondischarge tube to produce vertical blanking control impulses having aprodetcrmined amplitude and time duration, and an electron storagedevice connected between the anode of said second electron dischargetube and a point of fixed potential whereby voltage variations ofsubstantially sawtooth Wave form may be derived from the anode of saidsecond electron discharge tube.

OTTO H. SCHADE.

REFERENCES CITED The following references are of record in the :Eile ofthis patent:

.UNITED STATES PATENTS Number Name Date 1,587,520 Hartley June 8, 19262,153,217 Van der Mark Apr. 4, 1939 2,241,619 Sherman May 13, 19412,366,307 Anderson Jan. 2, 1945 2,368,448 Cook Jan. 30, 1945

